Generally, flux-gate type magnetic elements have high sensitivity when detecting a magnetic field and are capable of being reduced in size, as compared to Hall elements or magneto-resistive elements which are magnetic elements that detect similar magnetism. For this reason, flux-gate type magnetic elements are used in a magnetic field detector or the like such as a portable electronic device. Particularly, when magnetic balance type magnetic elements are used, it is possible to improve the accuracy of measurement.
In the magnetic balance type flux-gate type magnetic element, a time interval between detection signals is converted into time information indicating a time interval between PWM signals or the like, a time indicated by the time information is further converted into a DC voltage corresponding to a time length, and a feedback loop in which the DC voltage is set to a feedback signal is formed.
Therefore, a DC voltage obtained from a detection signal corresponding to a magnetic field to be applied is changed to an output signal indicating measurement results of the applied magnetic field. For this reason, it is necessary to inspect response characteristics in an internal circuit of a magnetic field detector.
That is, an output signal in a zero magnetic field is measured, thereby allowing an offset in the internal circuit which is superimposed on the output signal to be inspected. Here, when the response characteristics of the magnetic field detector are normal, a numerical value (within a range of a normal value in a predetermined specification) indicating a magnetic field of 0 is output as the output signal during the application of the zero magnetic field to the magnetic element. On the other hand, when there is abnormality in the response characteristics of the internal circuit of the magnetic field detector, the output signal is output with a deviation from a numerical value indicating a magnetic field of 0 during the application of the zero magnetic field to the magnetic element.
In addition, a magnetic field changing in a detectable magnetic field range shown in the specification of the magnetic field detector is applied, and an output signal in that case is measured, thereby allowing the linearity of a change in a time interval between detection signals with respect to a change in a magnetic field to be inspected. Here, when the response characteristics of the magnetic field detector are normal, a change in the detection signal has a linearity within the range of a normal value in a predetermined specification with respect to a change in a magnetic field. On the other hand, when there is abnormality in the response characteristics of the internal circuit of the magnetic field detector, a change in the detection signal does not have linearity with respect to a change in a magnetic field.
As described above, an offset in a zero magnetic field and the linearity of the output signal with respect to a change in a magnetic field are measured in the shipping inspection of the magnetic field detector, thereby allowing the quality determination of the magnetic field detector to be performed.
The zero magnetic field and a stationary magnetic field changing in a predetermined range are applied to the magnetic field detector with a high level of accuracy. For this reason, the magnetic field detector is inserted into a magnetic field generator that generates the stationary magnetic field, and the magnetic field detector is inspected by applying a predetermined magnetic field (see, for example, PTL 1).